When converting analogue telephone signals from a certain subscriber via a certain line, repeaters are used to provide two different signal paths. In one of these paths the analogue signals are coded to the PCM-coded signals and in the other a decoding of the digital PCM-coded signal flow is carried out. Furthermore, amplifiers are connected to compensate for the attenuation of the line. It is previously known to use a direct current magnetized hybrid transformer when dividing the input of the repeater towards the two-line, the transformer giving the desired current feeding to the subscriber's set connected to the line. At the same time, however, a DC-magnetizing of the transformer core is obtained.